Badges? We don't need no steekin' badges!
My, my, how things have changed. In my youth, no one at any casino would have invited ANY member of the 'G' into a casino. (In the past, the casino management would have handled this issue inhouse by strenously objecting to the competion, and the buzzards would find a fresh repast in the desert.)
It's private property. Owner requests law enforcement to enter property and check out suspicious activity. No warrant needed.
FBI agents failed to inform (tame?) judge of visit and evidence gathering (of unknown type, amount, etc) in the sworn affidavit for the warrant.
Judge recognizes the defect in the affidavit (probably after it was pointed out by a very expensive, but thurough defense attorney), and issues ruling.
Law enforcement takes note, and modifies it's behaviour appropriately (judge crossed off of 'tame' list).
BTW who benefited? The original perp walked, the perp's competition was rolled up, convicted & evicted, and the casino looks bad because it can't/won't keep confidential it's clientele's activities.